On-site, accurately and quickly to test the chloride content of concrete for

Establishing the chloride profile for
service life estimation

Establishing the depth of removal of a
chloride contaminated surface layer

Diagnosing a structure for corrosion
activity, e.g. in combination with the Mini Great Dane, the GalvaPulse and
the Rainbow Indicator

Monitoring the chloride content during
electrochemical removal of chlorides

Measuring the chloride content of fresh
concrete and/or its constituents

Principle

A sample of concrete is obtained by
drilling/grinding from the structure, or from the fresh concrete, mixed into a
distinct amount of extraction liquid and shaken for five minutes. The
extraction liquid removes disturbing ions, e.g. sulfide ions, and extracts the
chloride ions in the sample.

A calibrated electrode is submerged into the solution to
determine the amount of chlorides expressed as percentage of concrete mass.

The test is either the RCT
(Rapid Chloride Test) for acid soluble chlorides, or the RCTW (Rapid Chloride Test Water) for water-soluble
chlorides, using different kinds of extraction liquids. Both hardened and fresh
concrete can be tested with the system for chlorides.

Precision and accuracy

Numerous correlations have during the past
15 years been made between RCT and standard laboratory potentiometric titration
as the AASHTO T-260, ASTM C 144-81, DS 423.28 or NS 3671. Below are illustrated
such correlations made by various laboratories in the Scandinavian countries
and the USA.

In a recent comparison, the Swedish National Testing
Institute produced concrete powders containing known amount of chlorides
induced in the concrete by diffusion. The powders were made from concretes with
different binders as illustrated in the table below. Testing, according to
AASHTO T 260 standard laboratory potentiometric titration was done by five
certified Scandinavian laboratories, and by RCT in parallel.

The RCT readings were taken after the extraction samples
with dissolved concrete powder had been left over-night for full extraction.
Alternatively, if the result is needed after 5 minutes of shaking the vial, a
correction factor has to be applied.

The precision of the RCT compared to the known amount of
chlorides is as good as with the AASHTO T 260 potentiometric titration. The
average deviation of the RCT from the known amount of chlorides is within ± 4%.

For repeated testing with the RCT on the same concrete
powder the normal variation on the test results is in average ± 5%.

With the RCTW for water
soluble chlorides a similar close agreement as with the RCT, in terms of
precision and accuracy, has been found to standard titration tests in the
laboratory.

Testing examples

Chloride profiles measured with the RCT are
illustrated in the Profile Grinder section.

Adjacent is shown two other profiles,
obtained after profile grinding in-situ on a highway bridge column subjected four years to deicing salts. The concrete powders produced at depth increments of 1-2 mm were analyzed for acid soluble chlorides by the RCT and for water soluble chlorides with the RCTW. The depth of carbonation was measured with the Rainbow Indicator to be 2 mm, corresponding to the initial peaks of the chloride profiles produced.

Ordering numbers

RCT-500

The manual included in the RCT-500 kit covers testing for
acid and water-soluble chlorides of hardened as well as of fresh concrete.
Separately delivered is a binder (RCT-1100) with 15 years of testing
experience, included advanced theory for chloride diffusion modeling.

Extra Parts

RCT-1030 set of calibration liquids

RCT-1000-1 EWA

RCT-1032 Mixing Container and Cup

It is recommended always to have one extra set of clean
RCT-1030 set of calibration liquids at hand to make sure the chloride electrode
is working properly should deviations from the usual obtained calibration
values occur. The RCT-1000-1 EWA (Electrode Wetting Agent) contains 300 ml for
refill of the RCT-1000 EWA bottle with spout fitting the electrode hole.

The RCT-1032 mixing container and cup is for testing of
fresh concrete.

Consumables

The extraction liquids for RCT (acid soluble chlorides) are the following for
testing of hardened concrete and for testing of fresh concrete

RCT-1023 vials, set of 25,
for testing of hardened concrete

RCT-1031 vials, set of 25,
for testing of fresh concrete

Similarly, for RCTW (water
soluble chlorides) the extraction liquids are

RCTW-1023-1 vials, set of 25
RCTW-1023-2 buffer vials, set of 25,
for testing of hardened concrete

RCTW-1031-1 vials, set of 4
RCTW-1031-2 buffer vials, set of 4,
for testing of fresh concrete

Optional items

RCT-1032
balance for 1.5 gram, for checking the
powder weighing ampoules supplied in the RCT-500 kit